1. Field of Invention
The present invention relates to an inkjet head, and more particularly to an inkjet head that is provided with a piezoelectric actuator for ejecting ink.
2. Description of Related Art
An example of such kind of inkjet head is disclosed in U.S. Pat. No. 6,419,348, the disclosure of which is hereby incorporated by reference. The inkjet head disclosed in the above-mentioned U.S. patent has a cavity plate formed with a plurality of ink chambers and a laminated piezoelectric actuator. The piezoelectric actuator is bonded to the cavity plate so as to cover the openings of the ink chambers. The piezoelectric actuator is formed of multiple piezoelectric ceramic layers each made of lead zirconate titanate (PZT). On each layer of the piezoelectric ceramics, internal electrodes are discretely created. Further, a common electrode is provided so as to cover the top face of the piezoelectric actuator.
When driving signals are supplied to the internal electrodes, the piezoelectric ceramic layers distort in correspondence with the driving signals to cause pressure changes within the ink chambers. Based on these pressure changes, ink is ejected from nozzles of the inkjet head that are in fluid communication with the ink chambers.
Generally, the piezoelectric actuator for the inkjet head is produced by first laminating multiple green sheets of the piezoelectric layers with the internal electrodes interposed therebetween, providing the common electrode on the top of the obtained laminate of green sheets, and then sintering the same. The piezoelectric actuator, however, may become warped or deformed in a wavy form during the sintering process since the contraction percentage differs between the green sheets of the piezoelectric layers and the metals forming the electrodes. Such warp or deformation of the piezoelectric actuator may form a gap between the cavity plate and the piezoelectric actuator attached thereon, and such a gap may, in turn, cause leak of ink from the ink chambers.
Thus, there is a need for an inkjet head provided with a piezoelectric actuator that does not become warped or deformed during the sintering process thereof.